Field emitting devices are generally found in a variety of applications, such as flat panel displays (FPDs), ion guns, electron beam lithography, high energy accelerators, free electron lasers, electron microscopes and the like. A typical field emitting device includes a cathode and a plurality of field emitter tips, a grid closely spaced to the emitter tips and an anode spaced further from the cathode. Voltage induces emission of electrons from the tips, through the grid, toward the anode.
FIG. 1 is a simplified illustration of a conventional triode-type field emission device 100 including an emitter 102 for emitting electrons, a gate electrode 104 for controlling the amount of electrons generated from emitter 102, and an anode 106 positioned above the gate electrode 104. A current is selectively applied to emitter 102 from the source electrode 108, which is dependent on the voltage applied to the gate electrode 110 of the transistor. A high voltage for discharging electrons from emitter 102 is applied to the gate electrode 104.
The cathode material characteristics are important in predicting performance. Cathode materials are typically metal, such as Mo and the like, or semiconductor, such as Si and the like. For metal and semiconductor materials, the control voltage required for emission is relatively high. The high control voltage increases damage due to ion bombardment and surface diffusion on the cathode tips and necessitates high power densities to produce the required emission current density. The fabrication of uniform sharp tips has been heretofore difficult, tedious and expensive, especially over a large area.
Another type of emitter is known as nanoscale conductors have recently emerged as potentially useful electron field emitters. Nanoscale conductors are tiny conductive nanotubes (hollow) or nanowires (solid). Typically, nanoscale conductors are grown in the form of randomly oriented, needle-like or spaghetti-like powders that are not easily or conveniently incorporated into a field emitter device. Due to this random configuration, the electron emission properties are not fully utilized or optimized. Many nanoscale conductor tips may be buried in the mass.
Consequently, there is a need for an improved method of forming emitters for use in field emission devices.